Spinal implant with a flexible extension element

ABSTRACT

A spinal implant with at least one flexible elongated extension element is provided. The spinal implant has a profile that is lower than standard spinal implants. The spinal implant includes a bone anchor with a head portion and a shaft extending along a longitudinal axis of the bone anchor. A head plate is coupled to the bone anchor. The head plate includes a first elongated extension element and a second elongated extension element. The first elongated extension element and the second elongated extension element may be formed as a single monolithic element that is attached to the head plate by passing through a pair of openings provided on the head plate. At least one of the first elongated extension element and the second elongated extension element is flexible.

FIELD OF THE INVENTION

The present invention relates to spinal connection devices used inorthopedic surgery. More particularly, the present invention relates toa spinal implant with at least one flexible elongated extension element.

BACKGROUND OF THE INVENTION

Spinal fixation systems may be used in surgery to align, adjust and/orfix portions of the spinal column, i.e., vertebrae, in a desired spatialrelationship relative to each other. Many spinal fixation systems employa spinal rod, i.e. a spinal fixation element, for supporting the spineand for properly positioning components of the spine for varioustreatment purposes. The fixation system components, such as vertebralanchors, comprising pins, bolts, screws, and hooks, engage the vertebraeand connect the supporting rod to different vertebrae. The spinalfixation system components can have a predetermined contour that hasbeen designed according to the properties of the target implantationsite. Once installed, the spinal fixation system holds the vertebrae ina desired spatial relationship, either until desired healing or spinalfusion has taken place, or for some longer period of time. The size,length and shape of the spinal rod depend on the size, number andposition of the vertebrae to be held in a desired spatial relationshiprelative to each other by the apparatus.

Spinal fixation system components can be anchored to specific portionsof the vertebra. Since each vertebra varies in shape and size, a varietyof anchoring devices have been developed to facilitate engagement of aparticular portion of the bone. Pedicle screw assemblies, for example,have a shape and size that is configured to engage pedicle bone. Suchscrews typically include a threaded shaft that is adapted to be threadedinto a vertebra, and a head portion having a spinal fixationelement-receiving portion for receiving, for example, a spinal fixationrod. A set-screw, plug, cap or similar type of closure mechanism is usedto lock the spinal rod onto the rod-receiving portion of the pediclescrew. In use, the shaft portion of each screw is threaded into avertebra, and once properly positioned, the spinal fixation rod isseated through the rod-receiving portion of each screw.

Recently, the trend in spinal surgery has been moving toward providingminimally invasive elements and methods for implanting spinal fixationsystems. In some anchor devices, rigid extension elements are attachedto the heads of the anchor devices and extend out of the skin incision.These rigid extension elements may be used to control the head of theanchor device to assist the spinal fixation element in entering into thehead of the anchor device. The rigid extension elements limit the entryzone of the spinal fixation element into the head of the bone anchor.Thus the placement of the spinal fixation element into the bone anchorhead becomes very challenging. This is especially problematic inextended constructs where multiple vertebral bodies are being fixated.

One or more bone anchors may not be inserted immediately adjacent to thespinal fixation element. Additionally, in many instances one or morevertebrae may be out of alignment such that the one or more vertebraeand the inserted bone anchor are not immediately adjacent to theinserted spinal rod or the bone anchors do not have comparable heights.In these cases, since the spinal fixation rod cannot follow a wellaligned path, it becomes challenging or impossible to place the spinalfixation rod though each bone anchor. Specifically, in percutaneous orminimally invasive procedures, it is more difficult to adjust a spinalrod using a technique such as bending to make contact between the spinalrod and the bone anchors. It is also more difficult to move suchvertically or laterally displaced vertebrae so that the vertebrae may becoupled to the spinal rod.

Additionally, the current extension elements used in MIS procedurescause other logistical issues for the procedure. Extension elements thatcrowd the incision area add complexity to the operation. The timerequired managing assembling the extensions elements and disengagingthem may be extensive.

SUMMARY

Embodiments of the present invention may provide a bone anchor having ashaft to engage a bone. The bone anchor may have a head portion that isprovided above the bone. The bone anchor may be a poly-axial screw, amono-axial screw or a uni-screw. A head plate including a firstelongated extension element and a second elongated extension element maybe coupled to the bone anchor. The first elongated extension element andthe second elongated extension element may be formed as a singlemonolithic element that is coupled to the head plate by passing througha pair of openings provided on the head plate. A head cap may be coupledto the first elongated extension element, the second elongated extensionelement and the head plate. A spinal fixation element may be placed onthe head cap and stabilized between the head cap and a locking cap. Atleast one of the elongated extension elements is flexible. As usedherein, flexible refers to elements that are capable of being bent,flexed or twisted without unintentionally breaking.

The locking cap may slide along at least one of the elongated extensionelements. The locking cap may be lowered toward the head cap tostabilize the spinal fixation element therebetween using the elongatedextension elements. Alternatively, the locking cap may be lowered towardthe head cap using a set screw. The set screw may be coupled to thelocking cap. The elongated extension elements keep some of the softtissue around the surgical site away from the surgical site to provideclearance for the spinal fixation element. Thus, the surgeon may havebetter access to the surgical site and may controllably implant thespinal fixation element. The elongated extension elements may stick outof the surgical site. A portion of the elongated extension elements isremoved upon placing the spinal fixation element in a desired position.

According to a first aspect of the invention a spinal implant isprovided. The spinal implant includes a bone anchor, a head plate and ahead cap. The bone anchor has a head portion positioned above a bone anda shaft that extends along a longitudinal axis of the bone anchor. Theshaft is configured to engage a bone. The head plate is coupled to thebone anchor. The head plate includes a first elongated extension elementand a second elongated extension element. The first elongated extensionelement may be flexible. The first elongated element is provided on afirst side of the head plate. The second elongated extension element isprovided on a second side, across from the first side, of the headplate. The first elongated extension element and the second elongatedextension element may be provided as a single monolithic element thatpasses through a pair of openings provided on each side of the headplate. The head cap is coupled to the head plate, the first elongatedextension element and the second elongated extension element. The spinalfixation element is positioned on a seat portion of the head capprovided between the first elongated extension element and the secondelongated extension element.

According to various aspects of the present invention, the spinalimplant may also include an anchor locking cap adapted to move along atleast one of the first elongated extension element and the secondelongated extension element. The anchor locking cap is adapted to fitover the spinal fixation element so as to stabilize the spinal fixationelement between the seat portion of the head cap and the anchor lockingcap.

According to other aspects of the present invention, the spinal implantmay further include a plurality of reduction features provided on atleast one of the first elongated extension element and the secondelongated extension element. The plurality of reduction features providea controlled movement of the anchor head cap along at least one of thefirst elongated extension element and the second elongated extensionelement. The controlled movement prevents the anchor head cap fromsliding along the first elongated extension element or the secondelongated extension element.

According to another aspect of the present invention, a method forplacing a spinal fixation element over a bone anchor in a minimallyinvasive surgery is provided. The bone anchor has a shaft portionconfigured to be placed in a bone and a head portion configured to stayabove the bone. A first elongated extension element and a secondelongated extension element are coupled to a head plate by passing thefirst elongated extension element and the second elongated extensionelement through a pair of openings provided on the head plate. The boneanchor is coupled to the head plate when the shaft portion of the boneanchor is passed through a central opening provided on the head plate.The shaft portion of the bone anchor is inserted in a bone. The firstelongated extension element, the second elongated extension element andthe head plate stay above the bone. A head cap is coupled to the firstelongated extension element, the second elongated extension element andthe head plate. The first elongated extension element and secondelongated extension element pass through a pair of openings provided onthe head cap. The spinal fixation element is placed over a seat portionprovided on the head cap through a passage formed by the first elongatedextension element and the second elongated extension element. A lockingcap is placed over at least one of the first elongated extension elementand the second elongated extension element. The locking cap is reducedalong the at least one of the first elongated extension element and thesecond elongated extension element. The spinal fixation element isstabilized between the head cap and the locking cap.

According to various aspects, the method may also include removing aportion of the first extension element and/or the second extensionelement. The locking cap may be lowered using the first elongatedextension element and the second elongated extension element. The spinalfixation element may be provided at a distance above the seat portion ofthe head cap. The locking cap stabilizes the spinal fixation element inplace. The first elongated extension element and the second elongatedextension element may be flexible.

According to another aspect, the first elongated extension element isflexible and the second elongated extension element is substantiallyrigid. In this exemplary embodiment, the first elongated extensionelement may be placed through an opening provided on the secondelongated extension element so as to form a loop around the spinalfixation element. The locking cap locks to the head cap so as to enclosethe spinal fixation element and a portion of the first elongatedextension element forming the loop.

According to yet another aspect, a spinal implant is provided. Thespinal implant includes a head portion, a shaft and a head plate. Thehead portion is provided above a bone. The shaft is configured to engagethe bone. The head plate is coupled to the head portion and the shaft.The head plate includes a pair of extension sleeves for expanding anengagement area of a spinal fixation element with the head plate. Atleast one of the pair of extension sleeves is flexible. The pair ofextension sleeves has a shaped distal end providing a wider opening forthe spinal fixation element than a surface of the head plate.

BRIEF DESCRIPTION OF THE FIGURES

The foregoing and other objects, features and advantages of theinvention will be apparent from the following description and apparentfrom the accompanying drawings. The drawings illustrate principles ofthe invention and, although not to scale, show relative dimensions.

FIG. 1A illustrates how elements forming an exemplary spinal implantcouple together;

FIG. 1B illustrates elongated extension elements of the exemplary spinalimplant of FIG. 1A having a biased distal geometry;

FIGS. 1C-1F illustrate a closure mechanism of the exemplary spinalimplant of FIG. 1A stabilizing a spinal fixation element;

FIG. 2A illustrates how elements forming an exemplary spinal implanthaving a press fitting closure mechanism couple together;

FIG. 2B illustrates an elongated extension element of the exemplaryspinal implant of FIG. 2A having a biased distal geometry;

FIGS. 2C-2E illustrate a closure mechanism of the exemplary spinalimplant of FIG. 2A stabilizing a spinal fixation element;

FIG. 3A illustrates how elements forming an exemplary spinal implanthaving a dovetail closure mechanism couple together;

FIG. 3B illustrates an elongated extension element of the exemplaryspinal implant of FIG. 3A having a biased distal geometry;

FIGS. 3C-3E illustrate a closure mechanism of the exemplary spinalimplant of FIG. 3A stabilizing a spinal fixation element;

FIG. 4 illustrates an exemplary spinal implant with one flexibleelongated extension element and a substantially rigid elongatedextension element;

FIG. 5 is a flowchart of steps for positioning the spinal fixationelement in the exemplary spinal implant with a pair of flexibleelongated extension elements; and

FIG. 6 is a flowchart of steps for positioning the spinal fixationelement in the exemplary spinal implant with one flexible elongatedextension element and one rigid elongated extension element.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention may provide an improved spinalimplant with a profile that is lower than standard spinal implants to beused in minimally invasive surgeries. The spinal implant may include atleast one flexible elongated extension element. The spinal implant mayallow for controlled placement of a spinal fixation element. One skilledin the art will recognize that the invention is not limited to use inbone or in spinal surgery, and that the spinal implant and methodsdescribed herein can be adapted for use with any suitable surgicaldevice to be moved into a selected position in a variety of medicalprocedures.

FIGS. 1A-1F illustrate an exemplary spinal implant 100. The spinalimplant 100 includes a poly-axial or mono-axial screw 108. The screw 108includes a head portion 160 and a shaft 162 extending away from the headportion 160 along a longitudinal axis of the screw 108. The shaft 162 ofthe screw 108 engages a bone while the head portion 160 of the screw 108stays above the bone. According to various embodiments of the presentinvention, the screw 108 may be a uni-screw. The exemplary spinalimplant 100 further includes a head plate 106. The shaft 162 of thescrew 108 passes through a central opening 150 of the head plate 106such that the head portion 160 stays on a first side of the head plate106 and the shaft 162 stays on a second side, opposite to the firstside, of the head plate 106. The head plate 106 also includes a firstopening 152 and a second opening 154 provided on each side of thecentral opening 150. The exemplary spinal implant 100 also includes afirst elongated extension element 102 and a second elongated extensionelement 104. The first elongated extension element 102 may pass throughthe first opening 152 of the head plate 106 and the second extensionelement 104 may pass through the second opening 154 of the head plate106. Alternatively, the first elongated extension element 102 and thesecond elongated extension element 104 may be attached to or formedintegrally with the head plate 106.

According to the various embodiments of the present invention, the firstelongated extension element 102 and the second elongated extensionelement 104 may be formed as a single monolithic element by bending asingle extension element 170. The single extension element 170 may havea central opening 172 at the bent portion provided at the distal endthereof. The shaft 162 of the screw 108 may pass through the centralopening 172 of the single extension element 170 when the spinal implant100 is assembled as illustrated in FIG. 1A.

The exemplary spinal implant 100 illustrated in FIG. 1A further includesa head cap 126 that is coupled to the head plate 106. The head cap 126may be coupled to the head plate 106 by means of the first elongatedextension element 102 and the second elongated extension element 104.The head cap 126 may also be coupled to the head plate 106 by compressfitting, welding or any other feasible means. The head cap 126 mayinclude a central opening 150 to accommodate the head portion 160 of thescrew 108. The head portion 160 of the screw 108 may fit into thecentral opening 155 of the head cap 126. The head cap 126 may alsoinclude a first opening 156 and a second opening 158 provided on eachside of the central opening 155. The first opening 156 and the secondopening 158 of the head cap 126 may be aligned with the first opening152 and the second opening 154 of the head plate 106, respectively. Thefirst elongated extension element 102 may pass through the first opening156 of the head cap 126 and the second elongated extension element 104may pass through the second opening 158 of the head cap 126 to align thehead cap 126 to the head plate 106. According to various embodiments ofthe present invention, the head cap 126 may be formed integrally withthe head plate 106 of the exemplary spinal implant 100.

As illustrated in FIG. 1B, a distal end of the first elongated extensionelement 112 and a distal end of the second elongated extension element114 may have a biased geometry at a location closer to the head cap 126.A distance between the distal end of the first elongated extensionelement 112 and the distal end of the second elongated extension element114 may form a larger opening than the surface of the head plate 106.The biased distal geometry may be formed by providing a curve at thedistal ends 112 and 114 of the first elongated extension element 102 andthe second elongated extension element 104, respectively. The curve isformed by each elongated extension element curving outward, away fromthe other elongated extension element at the distal end thereof. Thebiased distal geometry allows a horizontal movement of the spinalfixation element 110 for easier placement and placement correction ofthe spinal fixation element 110. The biased distal geometry may beeliminated by placing a locking cap 116 over the distal ends of theelongated extension elements 112 and 114. When the biased distalgeometry, i.e. the curve, is eliminated, the elongated extensionelements 102 and 104 no longer have the curved shaped at theirrespective distal ends, 112 and 114. Alternatively, the biased geometrymay be eliminated by using a secondary tool.

The biased distal geometry may be formed during manufacturing of theelongated extension elements 102 and 104. The elongated extensionelements 102 and 104 may be made of biocompatible shape memory alloy,such as nitinol. The elongated extension elements 102 and 104 may bebent and shaped to acquire a desired form that provides a largerhorizontal opening between the distal ends 112 and 114 of the elongatedextension elements 102 and 104, respectively. The horizontal opening atthe biased distal geometry may be larger than the opening at theproximal ends of the elongated extension elements 102 and 104.

FIGS. 1C-1F illustrate the closure mechanism 180 according to anexemplary embodiment of the spinal implant 100. The closure mechanism180 may include a locking cap 116 and a set screw 120. The locking cap116 is provided around one or both of the elongated extension elements102 and 104. The locking cap 116 slides along the first elongatedextension element 102 and/or the second elongated extension element 104to stabilize the spinal fixation element 110 in place. Alternatively,the locking cap 116 may be driven toward the head cap 126 by the setscrew 120 along the first elongated extension element 102 and/or thesecond elongated extension element 104 to stabilize the spinal fixationelement 110 on a seat portion 124 of the head cap 126.

According to various embodiments of the present invention, the set screw120 may fit into the locking cap 116. The set screw 120 may be formedintegrally with the locking cap 116 such that the set screw 120 may befree to spin within the locking cap 116 without being able to bedetached therefrom. The set screw 120 may further keep the locking cap116 at a desired position. The set screw 120 may drive the locking cap116 toward the desired position. The set screw 120 may be set in placeusing a second tool, such as a screwdriver that mates with the set screw120. Setting the set screw 120 reduces the spinal fixation element 110toward the head cap 126 and prevents the locking cap 116 from movingalong a vertical direction over the first elongated extension element102 and the second elongated extension element 104.

According to various embodiments of the present invention, any of thefirst elongated extension element 102 and the second elongated extensionelement 104 may have surface features 122 that prevent the locking cap116 from uncontrollably sliding along the first elongated extensionelement 102 and/or the second elongated extension element 104. Thelocking cap 116 may mate with the surface features 122 to increasefriction between the locking cap 116 and the elongated extensionelements 102 and 104.

As illustrated in FIGS. 1D-1F, when the locking cap 116 is lowered, thespinal fixation element 110 is held in place between the seat portion124 of the head cap 126 and the locking cap 116. The surface 118 of thelocking cap 116 and the surface of the seat portion 124 facing thespinal fixation element 110 may be shaped to fit the shape of the spinalfixation element 110. For example, if the spinal fixation element 110 isa cylindrical spinal fixation element, the surface 118 of the lockingcap 116 and the surface of the seat portion 124 may be a concave surfaceto accommodate the convex outer surface of the cylindrical spinalfixation element.

When the exemplary embodiment illustrated in FIGS. 1A-1F is used with apolyaxial screw, the head portion 160 of the screw 108 may be heldwithin the head plate 106 and the shaft 162 of the screw 108 may rotateabout a central axis of the head plate 106. When a polyaxial screw isused, the set screw 120 pressing the spinal fixation element 110 ontothe seat portion 124 may also lock the polyaxial screw so as to restrictthe movement of the polyaxial screw within the head plate 106.

Sometimes, the spinal fixation element 110 may not be seated on the seatportion 124 due to spatial constraints. For example, the alignment ofthe vertebrae or the soft tissue at the surgical site may not allow thespinal fixation element 110 to be lowered all the way to be in physicalcontact with the seat portion 124. The spinal fixation element 110 mayalso be kept at a distance from the head cap 126 if the surgeon thinksthat the vertebra holding the spinal implant 100 may not handle theforce of reducing the spinal fixation element 110 to the seat portion124 the locking cap set screw 120.

In the exemplary embodiment illustrated in FIGS. 1A-1F, both of thefirst elongated extension element 102 and the second elongated extensionelement 104 are flexible. However, according to various embodiments ofthe present invention, the first elongated extension element 102 may beflexible and the second elongated extension element 104 may besubstantially rigid. Providing at least one flexible elongated extensionelement enables the surgeon to move the soft tissue around the skinincision away from the surgical site. The surgeon may also use theflexible elongated extension element to move the bone anchor, i.e. thescrew, or to create a larger pathway for the spinal fixation element. Aportion of the elongated extension elements may stay outside of theincision area. The extra portions of the elongated extension elementsmay be removed by cutting or disengaging the extension elements from thehead cap 106 upon completing the surgery.

The spinal implant 100 illustrated in FIGS. 1A-1F is implanted in apatient, under the skin. The first elongated extension element 102 andthe second elongated extension element 104 may stick out of the skinincision at the surgery site during the procedure. The portions of theextension elements staying above the skin enable the surgeon to locatethe spinal implants for placing the spinal fixation element 110 and/orfor placing the closure mechanism, e.g. the locking cap 116 or the setscrew 120, over the elongated extension elements 102 and 104. Theelongated extension elements 102 and 104 also keep the soft tissue awayfrom the incision site and provide a clear view of the surgical site tothe surgeon. The flexible elongated extension elements that stick out ofthe incision area may be bent to be parallel to the patient's skin toreduce crowding at the surgery site. Furthermore, extra portions of theelongated extension elements 102 and 104 are cut and removed ordisengaged above the locking cap 116 that remains implanted in thepatient.

FIGS. 2A-2E illustrate an exemplary spinal implant 200 with a press orsnap fitting closure mechanism 250. The exemplary spinal implant 200illustrated in FIGS. 2A-2E has a flexible elongated extension element302 and a substantially rigid elongated extension element 304. Bothelongated extension elements 302 and 304 may be integrally formed withthe head plate 306. Alternatively, the elongated extension elements 302and 304 may be coupled to the head plate 306 via a mechanicalconnection. According to yet another exemplary embodiment, thesubstantially rigid elongated extension element 304 may be formedintegrally with the head plate 306 and the flexible elongated extensionelement 302 may be coupled to the head plate 306. According to variousembodiments of the present invention, the flexible elongated extensionelement 302 and the substantially rigid elongated extension element 304may be provided with surface features 122, such as those illustrated inFIG. 1A, to help reduce a locking cap 316 along the elongated extensionelements 302 and 304.

In the exemplary embodiment illustrated in FIGS. 2A-2E, the locking cap316 is provided with a press fitting closure mechanism 250 forstabilizing the spinal fixation element 110 in place. The locking cap316 is lowered along the flexible extension element 302 and thesubstantially rigid extension element 304 and locked in place by merelypressing on the locking cap 316. The side sections of the locking cap316 couple to the side sections of the head plate 306. The locking cap316 is snapped in place as illustrated in FIG. 2C. The spinal fixationelement 110 may be securely held in place between the locking cap 316and the head plate 306. As illustrated in FIG. 2B, the head plate 306may include a saddle portion 308 that receives the spinal fixationelement 110. The spinal fixation element 110 is positioned on the saddle308 and locked in place using the press fitting closure mechanism 250.Alternatively, the press fitting closure mechanism 250 illustrated inFIGS. 2A-2E may be used with an exemplary embodiment where bothelongated extension elements are flexible.

The locking cap 316 may also include a set screw 320. The set screw 320,when reduced within the locking cap 316, may press the spinal fixationelement 110 onto the saddle 308. The exemplary embodiment illustrated inFIGS. 2A-2E may be used with a polyaxial screw where the head portion160 of the screw 108 may be held within the head plate 306 and the shaft162 of the screw 108 may rotate about a central axis of the head plate306. When a polyaxial screw is used, the set screw 320 pressing thespinal fixation element 110 onto the saddle 308 may also lock thepolyaxial screw so as to restrict the movement of the polyaxial screwwithin the head plate 306. According to various embodiments of thepresent invention, the exemplary embodiment illustrated in FIGS. 2A-2Emay be used with a uni-screw.

FIGS. 3A-3E illustrate an exemplary spinal implant 300 including adovetail closure mechanism 400 as another exemplary closure mechanism.In the exemplary embodiment illustrated in FIGS. 3A-3E, the exemplaryspinal implant 300 is provided with a substantially rigid elongatedextension element 404 and a flexible elongated extension element 402.According to various embodiments of the present invention, the elongatedextension elements may be both rigid, both flexible or any combinationthereof. Any of elongated extension elements 402 and 404 may beintegrally formed with the head plate 406. Alternatively, the elongatedextension elements 402 and 404 may be connected to the head plate 406via a mechanical connection. According to various embodiments of thepresent invention, the flexible elongated extension element 402 and thesubstantially rigid elongated extension element 404 may be provided withsurface features 122, such as those illustrated in FIG. 1A, to helpreduce a locking cap 416 along the elongated extension elements 402 and404.

The locking cap 416 may be placed over the substantially rigid elongatedextension element 404 and the flexible elongated extension element 402.The locking cap 416 may have a longer side section 412 and a shorterside section 414. The longer side section 412 of the locking cap 416fits over a shorter side section of the head plate 406. The shorter sidesection 414 of the locking cap 416 fits over a longer side section ofthe head plate 406 so as to form a dovetail closure mechanism 400. Thelonger side section 412 of the locking cap 416 has a tooth 422 that fitsinto a recess 408 formed on the head plate 406. The locking cap 416 islocked to the head plate 406 by pressing the tooth 422 into the recess408. A saddle element 410 may be coupled to the head plate 406 toreceive the spinal fixation element 110. The spinal fixation element 110is positioned on the saddle 410 and locked in place using the dovetailclosure mechanism 400.

In the exemplary embodiment illustrated in FIGS. 3A-3E, the locking cap416 may also include a set screw 420. The set screw 420, when reducedwithin the locking cap 416, may press the spinal fixation element 110onto the saddle 410. The exemplary embodiment illustrated in FIGS. 3A-3Emay be used with a polyaxial screw where the head portion 160 of thescrew 108 may be held within the head plate 406 and the shaft 162 of thescrew 108 may rotate about a central axis of the head plate 406. When apolyaxial screw is used, the set screw 420 pressing the spinal fixationelement 110 onto the saddle 410 may also lock the polyaxial screw so asto restrict the movement of the polyaxial screw within the head plate406. According to various embodiments of the present invention, theexemplary embodiment illustrated in FIGS. 3A-3E may be used with auni-screw.

FIG. 4 illustrates an exemplary spinal implant 400 with a flexibleelongated extension element 504 and a substantially rigid elongatedextension element 502. The flexible elongated extension element 504 andthe rigid elongated extension element 502 may be integrally formed withthe head plate 506. Alternatively, the elongated extension elements 502and 504 may be coupled to the head plate 506 via a mechanicalconnection. According to various embodiments of the present invention,the substantially rigid elongated extension element 502 and the flexibleelongated extension element 504 may be provided with surface features122, such as those illustrated in FIG. 1A, to help reduce a locking cap516 along the elongated extension elements 502 and 504.

The flexible elongated extension element 504 may fit through an opening508 provided on the substantially rigid elongated extension element 502forming a loop 512 over the spinal fixation element 110. The opening 508may include an engagement mechanism, such as a tooth, that engages theflexible elongated extension element 504 when the loop 512 is formed.The engagement mechanism may help to laterally reduce the spinalfixation element 110 when the flexible elongated extension element 504is pulled manually or using an instrument through the opening 508. Theloop 512 stabilizes the spinal fixation element 110 on a saddle portion524 coupled to the head plate 506 and prevents a lateral translation ofthe spinal fixation element 110. The locking cap 516 may slide on atrack 518 provided on the substantially rigid elongated extensionelement 502. The locking cap 516 is set in place when the locking cap516 slides into the recess 510 formed on the substantially rigidelongated extension element 502. The locking cap 516 may fit over theloop 512 to further stabilize the spinal fixation element 110. Thelocking cap 516 may include a tooth portion 514 provided at a distal endthereof. The tooth 514 may slide into a recess 515 provided on the headplate 506. The spinal fixation element 110 is positioned on the saddle516 and locked in place using the locking assembly 500. The locking cap516 sliding into the bottom recess 510 and the tooth portion 514 slidinginto the recess 515 may cause an extra portion of the flexible elongatedextension element 504 extending beyond the substantially rigid elongatedextension element 502 to detach from the head plate 506. An extraportion of the substantially rigid elongated extension element 502 maybe detached from the head plate 506 by cutting or using a snap-offfeature.

FIG. 5 is a flowchart of steps 600 for positioning the spinal fixationelement in the exemplary spinal implant with a pair of flexibleelongated extension elements. The exemplary spinal implant includes abone anchor, e.g. a bone screw, with a shaft portion implanted in a boneand a head portion provided above the bone. The bone anchor is coupledto a head plate by passing though a central opening of the head plate(step 602). The exemplary bone anchor may be a poly-axial screw, amono-axial screw and/or a uni-screw. A pair of flexible elongatedextension elements is also coupled to the head plate by passing throughopenings provided on each side of the head plate (step 604). The pair offlexible elongated extension elements may be integrally formed with thehead plate. Alternatively, the pair of flexible elongated extensionelements may be formed as a monolithic element that is placed throughthe openings of the head plate so as to form two elongated extensionelements. The pair of elongated extension elements is also coupled to ahead cap. The elongated extension elements pass through the openingsprovided on each side of the head cap. The openings of the head cap maybe aligned with the openings of the head plate. The head cap is providedon the head plate so as to compress the head plate and the head portionof the bone anchor. A spinal fixation element is placed on the head capbetween the pair of elongated extension elements (step 606). A lockingcap is placed over one or more elongated extension elements for lockingthe spinal fixation element in place between the locking cap and thehead cap (step 608). The locking cap is lowered along one or more of theelongated extension elements (step 610). According to one exemplaryembodiment, the pair of flexible elongated extension elements may bepulled away from each other to lower the locking cap along the pair ofelongated extension elements. According to another exemplary embodiment,a set screw may be provided through the locking cap. The set screw maybe threaded down to lower the locking cap along the pair of elongatedextension elements toward the head cap. Once the locking cap is loweredtoward the head cap, the spinal fixation element is stabilized betweenthe head cap and the locking cap (step 612). Therefore, the spinalfixation element is securely held in place. A portion of the elongatedextension elements may be provided above the skin incision at thesurgery site. At the end of the surgery, the portion of the pair ofelongated extension elements that stick out of the incision are easilyremoved by cutting or disengaging the elongated extension elements (step614).

FIG. 6 is a flowchart of steps 700 for positioning the spinal fixationelement in the exemplary spinal implant with one flexible elongatedextension element and one rigid elongated extension element. Theexemplary spinal implant includes a bone anchor with a shaft portionimplanted in a bone and a head portion provided above the bone. The boneanchor is coupled to a head plate by passing though a central opening ofthe head plate (step 702). A rigid elongated extension element and aflexible elongated extension element are also coupled to the head plate(step 704). The pair of elongated extension elements may be integrallyformed with the head plate. Alternatively, the pair of flexibleelongated extension elements may be coupled to the head plate by passingthrough the openings provided on each side of the head plate. Theelongated extension elements also coupled to a head cap by passingthrough the openings provided on each side of the head cap. The openingsof the head plate may be aligned with the openings of the head cap. Thehead cap is provided on the head plate so as to compress the head plateand the head portion of the bone anchor. A spinal fixation element isplaced on the head cap between the elongated extension elements (step706). A locking cap is placed over the rigid elongated extension elementfor locking the spinal fixation element in place (step 708). The lockingcap is lowered along the rigid elongated extension element toward thehead cap (step 710). The locking cap is provided to stabilize the spinalfixation element in place. According to an exemplary embodiment, it ispossible to further stabilize the spinal fixation element in place bymaking a loop over the spinal fixation element by placing the flexibleelongated extension element through an opening provided on the rigidelongated extension element (step 712). Then the locking cap may belocked in placed over the loop, stabilizing the spinal fixation elementin place (step 714). Therefore, the spinal fixation element is securelyheld in place between the locking cap and the head cap. A portion of theelongated extension elements may be provided above the skin incision atthe surgery site. At the end of the surgery, the portion of the pair ofelongated extension elements that stick out of the incision are easilyremoved by cutting or disengaging the elongated extension elements fromthe head portion (step 716).

According to various embodiments of the present invention, the pair ofelongated elements may have a biased distal geometry. The biased distalgeometry may have a larger opening than a surface of the head plate ofthe spinal implant. The biased distal geometry allows for the horizontalmovement of the spinal fixation element.

The flexible elongated extension elements described herein may beconstructed of any biocompatible material including, for example,plastic, nitinol to allow for a biased geometry to allow vertebralcorrection and easier placement of the spinal fixation element. Therigid elongated extension elements described herein may be constructedof metal, such as titanium, stainless steel, polymers, ceramics, orcomposites thereof.

The present invention is described above relative to certain exemplaryembodiments to provide an overall understanding of the principles of thestructure, function, manufacture, and use of the spinal implantdisclosed herein. Those skilled in the art will appreciate that thepresent invention may be implemented in a number of differentapplications and embodiments and is not specifically limited in itsapplication to the particular embodiments depicted herein.

A person having ordinary skill in the art will appreciate that theaforementioned methods and implants can be modified depending on thetype of anchor being used, as well as the specific procedure beingemployed. Moreover, other methods and devices known in the art can beused in accordance with the present invention.

One skilled in the art will appreciate further features and advantagesof the invention based on the above-described embodiments. Accordingly,the invention is not to be limited by what has been particularly shownand described, except as indicated by the appended claims.

While the instruments and methods disclosed herein have beenparticularly shown and described with reference to the exemplaryembodiments thereof, those of ordinary skill in the art will understandthat various changes may be made in the form and details herein withoutdeparting from the spirit and overall scope. Those of ordinary skill inthe art will recognize or be able to ascertain many equivalents to theexemplary embodiments described specifically herein by using no morethan routine experimentation. Such equivalents are intended to beencompassed by the overall scope and the appended claims

1. A method of placing a spinal fixation element over a bone anchor in aminimally invasive surgery, the bone anchor having a shaft portionconfigured to be placed in a bone and a head portion configured to stayabove the bone, the method comprising: coupling a first elongatedextension element and a second elongated extension element to a headplate by passing the first elongated extension element and the secondelongated extension element through a pair of openings provided on thehead plate; coupling the bone anchor to the head plate by passing theshaft portion of the bone anchor through a central opening provided onthe head plate; inserting the shaft portion of the bone anchor in abone, wherein the first elongated extension element, the secondelongated extension element and the head plate stay above the bone;coupling a head cap to the first elongated extension element, the secondelongated extension element and the head plate, wherein the firstelongated extension element and second elongated extension element passthrough a pair of openings provided on the head cap; placing the spinalfixation element over a seat portion provided on the head cap through apassage formed by the first elongated extension element and the secondelongated extension element; placing a locking cap over at least one ofthe first elongated extension element and the second elongated extensionelement; reducing the locking cap along the at least one of the firstelongated extension element and the second elongated extension element;and stabilizing the spinal fixation element between the head cap and thelocking cap.
 2. The method of claim 1, wherein at least one of the firstelongated extension element and the second elongated extension elementcomprises a plurality of reduction features to prevent the locking capfrom sliding along the first elongated extension element and the secondextension elongated element.
 3. The method of claim 1 furthercomprising: removing a portion of the first elongated extension elementor the second elongated extension element.
 4. The method of claim 1,wherein reducing the locking cap further comprises: using the firstelongated extension element and the second elongated extension elementto lower the locking cap, wherein the first elongated extension elementand the second elongated extension element are flexible.
 5. The methodof claim 1, wherein stabilizing the spinal fixation element furthercomprises: providing the spinal fixation element at a distance above theseat portion of the head cap, the locking cap stabilizing the spinalfixation element in place.